I spent much of the past year hospitalized after a bad car accident, during which I played a lot of DW. As the Timurids, I managed to conquer the Middle-East, North Africa, East Africa, India, the Balkans, Italy, Hungary, and Poland by ~1420, when I became the Mughals. I also conquered Chagatai, the Oirats, Kazakhs, and much of the Golden Horde, which allowed me to use standard diplomacy to take provinces. I used monthly auto-saving and reloaded whenever Timur died until after I changed tags (Timur died in 1426). Yes, I recognize that is a cheese tactic. After the tag change, I switched governments to become an Empire, and used the Holy War CB to conquer the provinces along the Atlantic coast. Since I took out nearly all Muslim powers while a Horde, I had access to the Holy War CB against everyone except the Islamic nations in Indonesia, which means that nearly every province was acquired for either 0 infamy (when I was a Horde taking non-Horde provinces), 1 infamy (using the Holy War CB), or 2 infamy (using the Tribal Feud? CB). The potential colonist bottleneck was avoided by conquering nearly all Horde provinces while a Horde myself. Also, starting as the Timurids (this would also apply to any Horde other than GOL) means the earliest you can build ships with easy access to the Mediterranean/Atlantic is 1452 (conquer a province along the Black Sea in 1400, ~2 years for it to flip, then 50 years for it to core and allow ship-building). In particular, this means that Britain has a good chance to start colonizing the Americas before you can do anything about it. Note, I did not make the WC until after 1600, bu had I used more save cheese to avoid nasty events and regency councils then it would have been much earlier.
In any event, the issue that cropped up for me was revolts and money. Continuously expanding that quickly means a large amount of time will be spent with uncored heatens provinces that have nationalism while suffering from Overextension. The first issue arising from those factors is that you'll have absurd revolt risk nearly everywhere, even if you're playing smart and keeping your WE low. That means that you need a significant percentage of your forces kept stationed around your nation to crush the revolters. This ties in to the second issue, money. Uncored, heathen, wrong culture provinces do not provide much in the way taxes. If your fighting wars against a Ming that has conquered nearly all of eastern and south-eastern Asia, Britain, France, Spain, and Portugal, that's a lot of troops that you need beyond the anti-rebel stacks. Troops and ships cost money, and you're not getting very much relative to your size. Neither is crippling, but it necessitates huge amounts of micro. Note, however, that while still a Horde, nearly every ducat you can spare needs to go into Government tech, and thus you need to avoid inflation like the plague and frequently convert 200 ducats into 100 research. Then, when you're no longer a Horde, you need to focus on Trade tech like there's no tomorrow to get QFTNW and be able to conquer the Americas and Africa before you hit 1500.
I'd wager that if you're going for a WC by 1500, a Horde is definitely your best bet, and possibly your only bet. In particular, the Timurids start off with good positioning to expand against same-religion nations while a Horde and then switch to the Mughals before Timur dies, but run the risk of Britain, Norway (via Iceland), and the Irish minors colonizing before you can reach them. The Golden Horde would provide for earlier access to ships that can reach the north Atlantic and conquer Britain, Ireland, and Iceland before they can colonize, but will struggle with conquering all Islamic nations before needing to switch tags. The biggest challenge as a horde, though, is reaching Gov 4 before your ruler dies.
Anyways, I think that a WC by 1500 could be possible, but it would involve huge amounts of micro and some luck. I'd also expect that only a few countries start off with enough natural advantage to make it feasible. Obviously, I'd give the Timurids and Golden Horde as the two that are most likely for success, and then I'd wager that England, Castille, Hungary, Muscovy (thanks to its missions allowing it to form Russia pretty quickly, giving lots of free cores to gobble for 0 infamy), and France all have natural advantages and missions that would make this potentially feasible. No matter who is picked, I doubt it would be possible without some amount of save cheese to avoid regency councils and crushingly bad events.
I'm sure that OP has figured out by now that WC in DW is definitely doable.
